Handwritten code made with EditPlus

   A collection of even more JRC NRD-515    
diagrams and modifications


Links to more JRC LOGO information:


  Most of the PDF diagram information is already on the internet, but in versions I dislike. Too low resolution, too much grey or unneeded 16 million colors information, or with nasty stains. PDF's over here are optimised where possible, cleaned and edited versions.

And with additional repair, update and alignment info.

Item Highres TIF
in PDF file
JST-100 diagrams from the Instruction Manual
Power supply unit Instruction Manual for the NBD-500. The JST-100 or JST-125 (20 amps, first version) supply unit. Completely stuffed and edited version.
See further down info for a "struck by lightning" repair of this unit with a few pictures.

The original schematic as a single page, with 300% multiplied resolution and BW conversion
It is so nice that I also added it as an extra page in the above manual

After rebuild: my new schematic, graphically edited in real JRC sybols, made from the above version

A datasheet of the power cannon transistors 2SD717





A datasheet for the original 110V AC power supply relay RH1V2-U.
A datasheet for the 12V DC power supply relay I used, the G2R-1.
Power supply unit Instruction Manual for the NBD-520
A newer / later (30 amps) supply unit for the JST-100, JST-125 or JST-135 .

The scan of the drawing is too small and therefore so bad that I made a complete re-drawn 200% version!



JST-125 diagrams from the Instruction Manual
Completely stuffed and edited version
JST-135 Instruction Manual
NON stuffed original - bad scan....
JST-135 Service Manual
A completely redone scan now in perfect quality! PE1ABR edited version.
JST-145 and JST-245 Service Manual
Complete 165 page PE1ABR edited version
Most simple frequency alignment for the JST-100 and JST-125 if the SSB sounds strange or unnatural.
Check and align only the 10 and 70 MHz ref and the PBT and HF compression mixer oscillator on 9.155 MHz, NOTHING else.
Instruction manual part 1 for the NRD-91, all edited and cleaned. ONLY standard A4 pages.
Easier for printout.

Instruction manual part 2 for the NRD-91, all edited and cleaned. ONLY large A3 pages.
Some cut in half pages are graphically merged again! No glue needed. Ideal if you print them on full size in a copyshop. So also easier for printout.

I made a nice NRD-91 front for the book, one page in color.




The complete JRC NRD-525 Service manual


A very old JRC rack mount NSD-51 transmitter for use on a ship. 1500 Watt output, 3-phase power supply. Complete manual with diagrams

A cleaned version of the datasheet of the used power beam tetrode 8122. Three of them are in parallel.



Click over   HERE   for lots of PDF files about hardware
used in the JRC and in my own designs.

Repair of a blown NBD-500, or better: a complete rebuild

Repair of a NBD-500 burnt out supply after lightning flash-over in the transformer. Apart from also a lot of damage in the JST-100. Is it hopelessly damaged? Or is there any chance for success?

A "standard" transformer is simply not available, so an attempt was made to place a hughe modern mains toroid transformer in the cabinet. To avoid big mounting bolts sticking out of the cabinet and maintain airflow, an assembly seat was made for flat / horizontal mount. This also doesn't obstruct the normal airflow slits. Vertical mount didn't fit at all. Due to a big lack of space the circuit board also got a different position.
Also added a set of inrush reducing NTC R's and a VDR to absorb switch-off spikes.
The switch-on with a relay is now realised with a much safer approach. I used a little second low voltage transformer to keep the on-off switch circuit separated from hot mains.
The toroid manufacturer output already had taken account for voltage drop, I also did when ordering a Amplimo 88043 toroid with 2x 17V AC. So the voltage was a little too high!! To reduce heat a negative winding is added (4 wires 1.5 sq. mm in parallel) to lower the secondairy output a little. By using 0.5 V per winding, I added 3 windings to reduce it with 1.5 V AC.
It seems also possible now to use a toroid with 2x 15V AC and to ADD one or two windings if a little higher voltage is needed!

If you have to make a decision yourself, the possibilities are:

Amplimo__77045       300VA - 2x 16V - 2x 9.37A
Amplimo__78043       300VA - 2x 17V - 2x 8.82A
Amplimo__88013       500VA - 2x 15V - 2x 16.7A
Amplimo__88043       500VA - 2x 17V - 2x 14.7A
Where have the mains tracks gone......

300 VA is too weak and AC will drop too much. It also should be a little over dimensioned to avoid overheating. Don't forget to use 2x a NTC type NTC5 (= 2x 5 Ohm) in series and a VDR directly over the mains winding!
Take care: the NTC's become HOT, use a glassfiber cover board, and the VDR might explode, so encapsulate it in shrink tube. See the pictures below.

Epilog: the mains voltage tracks crawling through the circuitboards inside the JST-100 is/was unwise by design. The tracks were all vaporised. And a flashover in the on-off switch to the circuit of the 74LS123. This IC was also blown, happily not more. One on-off switch section was for mains, the second for internal on-off (timer-)control.
By using an additional modified small (adapter) transformer for making the 12V DC and a new low voltage relay (with 16 amp contacts!) for the on-off circuit it is a lot safer now. The extra transformer is situated between the big electrolyte and the board, it's a small black block with removed mains contact pins. The new on-off circuit is galvanically separated from everything, but has a static discharge to ground!

See the extra PDF drawing, made graphically with original JRC symbols. Now it looks like JRC drew it themselves!
And YES, all is working again!

Top view, the tin can has a car bulb in water and a light shield = 2x 60W dummy load.
It's an adjustable 2.5, 5 or 10 Amp dummy!
Side view, see 4x parallel negative winding

Watch new location control board and mounting bracket, VDR and NTC's

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by Walter - PE1ABR - 2020-06-29